Predictive and Therapeutic Implications of a Novel PLCγ1/SHP2-Driven Mechanism of Cetuximab Resistance in Metastatic Colorectal Cancer.

PURPOSE: Cetuximab is an EGFR-targeted therapy approved for the treatment of RAS wild-type (WT) metastatic colorectal cancer (mCRC). However, about 60% of these patients show innate resistance to cetuximab. To increase cetuximab efficacy, it is crucial to successfully identify responder patients, as well as to develop new therapeutic approaches to overcome cetuximab resistance. EXPERIMENTAL DESIGN: We evaluated the value of EGFR effector phospholipase C gamma 1 (PLCγ1) in predicting cetuximab responses, by analyzing progression-free survival (PFS) of a multicentric retrospective cohort of 94 treated patients with mCRC (log-rank test and Cox regression model). Furthermore, we used in vitro and zebrafish xenotransplant models to identify and target the mechanism behind PLCγ1-mediated resistance to cetuximab. RESULTS: In this study, levels of PLCγ1 were found increased in RAS WT tumors and were able to predict cetuximab responses in clinical samples and in vitro and in vivo models. Mechanistically, PLCγ1 expression was found to bypass cetuximab-dependent EGFR inhibition by activating ERK and AKT pathways. This novel resistance mechanism involves a noncatalytic role of PLCγ1 SH2 tandem domains in the propagation of downstream signaling via SH2-containing protein tyrosine phosphatase 2 (SHP2). Accordingly, SHP2 inhibition sensitizes PLCγ1-resistant cells to cetuximab. CONCLUSIONS: Our discoveries reveal the potential of PLCγ1 as a predictive biomarker for cetuximab responses and suggest an alternative therapeutic approach to circumvent PLCγ1-mediated resistance to cetuximab in patients with RAS WT mCRC. In this way, this work contributes to the development of novel strategies in the medical management and treatment of patients with mCRC.

Platinum-Triggered Bond-Cleavage of Pentynoyl Amide and N-Propargyl Handles for Drug-Activation.

The ability to create ways to control drug activation at specific tissues while sparing healthy tissues remains a major challenge. The administration of exogenous target-specific triggers offers the potential for traceless release of active drugs on tumor sites from antibody-drug conjugates (ADCs) and caged prodrugs. We have developed a metal-mediated bond-cleavage reaction that uses platinum complexes [K2PtCl4 or Cisplatin (CisPt)] for drug activation. Key to the success of the reaction is a water-promoted activation process that triggers the reactivity of the platinum complexes. Under these conditions, the decaging of pentynoyl tertiary amides and N-propargyls occurs rapidly in aqueous systems. In cells, the protected analogues of cytotoxic drugs 5-fluorouracil (5-FU) and monomethyl auristatin E (MMAE) are partially activated by nontoxic amounts of platinum salts. Additionally, a noninternalizing ADC built with a pentynoyl traceless linker that features a tertiary amide protected MMAE was also decaged in the presence of platinum salts for extracellular drug release in cancer cells. Finally, CisPt-mediated prodrug activation of a propargyl derivative of 5-FU was shown in a colorectal zebrafish xenograft model that led to significant reductions in tumor size. Overall, our results reveal a new metal-based cleavable reaction that expands the application of platinum complexes beyond those in catalysis and cancer therapy.

The histone acetyltransferase hMOF promotes vascular invasion in hepatocellular carcinoma.

BACKGROUND & AIMS: Vascular invasion is a major prognostic factor in hepatocellular carcinoma (HCC). We previously identified histone H4 acetylated at lysine 16 (H4K16ac), a histone modification involved in transcription activation, as a biomarker of microvascular invasion (mVI) in HCC. This study aimed to investigate the role of hMOF, the histone acetyltransferase responsible for H4K16 acetylation, in the process of vascular invasion in HCC. METHODS: hMOF expression was assessed by RT-qPCR and immunohistochemistry in a retrospective series of HCC surgical samples, and correlated with the presence of mVI. The functional role of hMOF in HCC vascular invasion was investigated in vitro in HCC cell lines using siRNA, transcriptomic analysis and transwell invasion assay, and in vivo using a Zebrafish embryo xenograft model. RESULTS: We found that hMOF was significantly upregulated at the protein level in HCC with mVI, compared with HCC without mVI (P < .01). Transcriptomic analysis showed that hMOF downregulation in HCC cell line lead to significant downregulation of key genes and pathways involved in vascular invasion. These results were confirmed by transwell invasion assay, where hMOF downregulation significantly reduced HCC cells invasion. Finally, hMOF downregulation significantly reduced tumour cell intravasation and metastasis in vivo. CONCLUSIONS: Altogether, these results underpin a critical role for hMOF in vascular invasion in HCC, via transcription activation of key genes involved in this process. These data confirm the major role of epigenetic alterations in HCC progression, and pave the way for future therapies targeting hMOF in HCC.